An apparatus for axially positioning a roll of a rolling mill is known comprising a hydraulic positioning means for the axially positioning at least one of the rolls of a roll pair and a control device for position control of the hydraulic positioning means to fix the axial position of the roll using a set point value/actual value comparison.
The setting and maintaining of a certain axial relative position of the cooperating rolls is of significance for rolling precision and the rectilinear course of the rolled material in regard to the axial forces arising in a roll pass, especially with an unsymmetrical profile of the workpiece. That is also true for the horizontal rolls of a universal rolling mill since the tolerances of the flange thickness of parallel mounted flanges can be disadvantageously effected by any relative axial shifting of the horizontal rolls. However tolerances must also be maintained for flange thicknesses in the rolling of bulkhead profile or steel structural shapes in a two high rolling mill.
Apart from manually operated axial positioning devices, these are known positioning mechanisms driven by an electric motor. One known axial positioning device engages on a journal block of a roll in which the roll is secured axially or on the roll itself which is axially movable in the radial bearing of the axially nonslidable supporting member. The positioning mechanism can engage also on a separate axial bearing and/or its bearing housing.
A disadvantage of the known axial positioning device for the rolls of a rolling mill for making a steel profile or steel structural shape is that it can be operated only between passes. The axial forces originating from the pass vary frequently just during rolling and, since the positioning apparatus must be supported in one roll stand, relative shifting is unavoidable during a roll pass because of compressibility in the roll and the positioning means.
The rolled material shape and the rolled material course can be undesirably influenced by an open roll design. This disadvantage can be compensated in rolling by unsymmetrically shaped rolls by a supporting collar or flange on the upper and the lower rolls which hold these rolls fixed in position relative to each other. Friction on the supporting collars however leads to higher energy and rolling costs. In recent years the field of slab rolling or flat rolling devices for axially shifting rolls opposite to each other have become known including double acting hydraulic cylinders which can be operated during rolling (German Pat. No. 24 40 495). This hydraulic axial positioning device has a higher flexibility with high axial forces on the rolls which may not be problematical in flat or slab rolling but cannot be tolerated in the rolling of structural shapes.